<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        var arr = ["a","b","c","d"];
        var arr1 = ["aa","bb"];
        var arr2 = arr.concat(arr1,[12,23]);
        console.log(arr2);

        arr = [12,23,54,45,56];
        arr1 = arr.filter(function(item,index,array){
            return item > 30;
        })
        console.log(arr1);

        arr1 = arr.find(function(item,index,array){
            return item > 30;
        })
        console.log(arr1);

        arr1 = arr.findIndex(function(item,index,array){
            return item > 30;
        })
        console.log(arr1);

        arr1 = arr.map(function(item,index,array){
            return item + 2;
        })
        console.log(arr1);

        arr1 = arr.reduce(function(a,b){
            return a + b;
        })
        console.log(arr1);

        arr.forEach(function(item,index,array){
            console.log(item,index,array);
        })

        var res = arr.includes("b");
        console.log(res); //
    </script>
</body>
</html>